Drive unit with an internal combustion engine and an exhaust gas turbocharger

ABSTRACT

The invention relates to a drive unit, comprising an internal combustion engine with a crankshaft; an exhaust line; an exhaust gas turbine which is acted on by the exhaust gas line, which is arranged downstream of the internal combustion engine and has the purpose of transmitting a positive torque to the crankshaft in the traction mode; a hydrodynamic unit which is arranged downstream of the exhaust gas turbine and has two turbine blades which form a torus-shaped working chamber; the hydrodynamic unit has a drive connection to the drive train; and a parking brake is provided for securing the primary turbine wheel of the exhaust gas turbine.

FIELD OF THE INVENTION

The invention relates to a drive unit comprising an internal combustionengine.

BACKGROUND

DE 195 16 97 describes a drive unit having an internal combustion enginehaving turbocompound design. In this unit, a turbine is provided towhich exhaust gas is fed from the internal combustion engine during thetraction mode in order to drive the turbine. The turbine has a driveconnection to the crankshaft via a hydrodynamic clutch. In this way itis possible to utilize the residual energy still present in the exhaustgas.

In the aforesaid drive unit, a further exhaust line is connecteddownstream of the turbine. An exhaust valve is provided in this exhaustline. At the changeover from the traction mode to the braking mode, theexhaust valve is closed. As a result, an exhaust gas pressure whichcauses the exhaust valve to open when a certain value is reached buildsup behind the turbine.

DE 37 28 681 C2 and DE 39 04 399 A1 also describe drive units withdevices for recovering exhaust gas energy.

Drive units of this type have the advantage that the residual heat whichis contained in the exhaust gas is utilized—if appropriate after theexhaust gas has passed through an exhaust gas turbocharger. However,said drive units do not contribute directly to the braking in brakingmode. The aforesaid exhaust valve performs the customary exhaust gasbraking throttling which is known per se.

The invention is based on the object of configuring a drive unit of theaforesaid type in such a way that not only the residual energy containedin the exhaust gas is utilized in the traction mode but also in such away that the drive unit contributes to the braking in the braking mode.

SUMMARY OF THE INVENTION

Accordingly, the hydrodynamic unit is configured in a particular waywith the two turbine blades. The two turbine blades are in factconfigured and arranged in such a way that they can operate as rotors.Here, their structure is basically the same as that of turbine blades ofa hydrodynamic clutch or of a retarder. The difference with respect to ahydrodynamic clutch or with respect to a retarder is however the factthat one of the two rotors can be fixed or secured against rotation. Thetwo rotors are arranged in one housing. The working space is filled witha fluid medium, for example with water or with oil. Any type of lockingdevice, for example a multi-disc clutch, can be used to lock one of thetwo rotors.

Such a drive unit operates as follows:

In the traction mode, that is to say when the motor is circulating underload, both rotors of the hydrodynamic unit rotate as neither of therotors is fixed in terms of rotation. One rotor is driven by theturbine, and said rotor itself drives the other rotor, which thussupplies torque to the drive train. The hydrodynamic unit thus operatesas an entirely conventional hydrodynamic clutch. Accordingly, it has itsadvantages, namely gentle starting up which is largely free of torquesurges. This applies not only when starting up but also during theentire traction mode. The load peaks are buffered in this way.

If the vehicle changes from the traction mode to the braking mode, oneof the two rotors is stopped so that torque cannot be transmitted to thedrive train any more. Instead, torque is removed from the drive train.In this process, that rotor which is located on the side of thehydrodynamic unit facing the turbine is stopped (primary wheel).

As an alternative to stopping (braking) the one rotor, other measureswhich intervene in the working of the hydrodynamic unit and which leadto the torque flux being interrupted are also conceivable.

The primary wheel is best braked by means of a parking brake, forexample a multi-disc clutch.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail with reference to the drawingin which the following is illustrated:

FIG. 1 shows a schematic view of a drive unit according to a firstembodiment,

FIG. 2 shows a schematic view of a drive unit according to a secondembodiment,

FIG. 3 shows a drive unit in which the individual components areillustrated somewhat more specifically.

DETAILED DESCRIPTIONS

The drive unit according to the first embodiment which is illustratedschematically in FIG. 1 comprises an exhaust gas turbine 3. The exhaustgas stream of an engine (not shown here) is applied to said exhaust gasturbine 3. The exhaust gas turbine 3 is however not a component of anexhaust gas turbocharger. An exhaust gas turbocharger may be connectedupstream of the aforesaid exhaust gas turbine 3.

A hydrodynamic unit 4 is also shown. Said hyrodynamic unit 4 has aprimary turbine wheel 4.1 and a secondary turbine wheel 4.2. The twoturbine wheels are configured like the turbine wheels of a hydrodynamicclutch or of a hydrodynamic brake. However, both turbine wheels arebasically freely rotatable. A parking brake 4.5 is assigned to theprimary wheel 4.1. In this way the primary wheel 4.1 can be locked.

A sensor 101 may be provided to sense the operating state of the engine(i.e., normal mode or braking mode) and supply a corresponding signal toa central process unit 106. The central processor unit 106 may thencontrol the parking brake 4.5 via an actuator device 116 for securingthe primary wheel 4.1 in the braking mode.

It is apparent that the exhaust gas turbine 3 has a mechanical driveconnection to the primary turbine wheel, specifically via a drive shaft3.1, a first gear train 5 and a drive shaft 4.1.1.

The secondary turbine wheel 4.2 is connected fixed in terms of rotationto a further drive shaft 4.2.1. The latter operates on a second geartrain 6, which in turn has a drive connection to a shaft 7. The shaft 7operates on the crankshaft or on another energy consuming device, forexample, a fan wheel.

During normal driving when the engine circulates under load, exhaust gasis fed to the exhaust gas turbine 3. The parking brake 4.5 is notfunctioning so that the two wheels 4.1, 4.2 can rotate freely. Theexhaust gas stream is applied to the exhaust gas turbine 3 so that itgenerates torque which is fed to the primary wheel 4.1 and causes it torotate. As a result of the working fluid contained in the working spaceof the hydrodynamic unit 4, torque is transmitted to the secondary wheel4.2 and from there to the crankshaft 7 or to another energy consumingdevice.

During the braking mode, only a small exhaust gas stream occurs in anycase. This is diverted so that it does not act on the turbine 3. Theparking brake 4.5 is actuated so that the primary wheel 4.1 is secured.The hydrodynamic unit 4 thus becomes a retarder. If the shaft 7 has adrive connection to the crankshaft, the device illustrated contributesto the braking.

The drive unit of the secondary embodiment which is illustrated in FIG.2 has a similar design to the drive unit of the first embodiment.However, the hydrodynamic unit 4 comprises a hydrodynamic brake 4.1, 4.2(retarder), and a hydrodynamic clutch 4.3, 4.4.

The turbine wheel 4.1 of the retarder forms the stator here, and theturbine wheel 4.2 the rotor.

The two wheels 4.3, 4.4 of the clutch are freely rotatable. The wheels4.2 of the retarder and 4.3 of the clutch are connected fixed in termsof rotation to one another so that they rotate together. They may evenbe embodied as a single cast part.

Moreover, in the drive unit of the second embodiment, the same orsimilar elements are present like those in the drive unit of the firstembodiment, with the exception of the parking brake 4.5 of the firstembodiment, which is absent in the second embodiment.

The drive unit of the second embodiment operates as follows:

In the traction mode, the working space of the retarder 4.1, 4.2 isempty, while the working space of the clutch 4.3, 4.4 is filled with aworking medium, generally an oil.

An exhaust gas stream is applied to the exhaust gas turbine 3 from theinternal combustion engine (not illustrated here). The exhaust gasturbine 3 drives the first gear train 5 via the shaft 3.1, and the shaft4.1.1 drives the primary wheel 4.4 of the clutch. Said primary wheel 4.4transmits torque to the tandem unit, formed from the secondary wheel 4.3of the clutch and the wheel 4.2 of the retarder. These two wheels areconnected to one another fixed in terms of rotation and form what isreferred to as a back-to-back unit. From there, torque is transmittedonward via the shaft 4.2.1 and the second gear train 6 to the crankshaft7.

During the braking mode, the working space of the retarder 4.1, 4.2 isfilled. The working space of the hydrodynamic clutch 4.3, 4.4 remainsfilled. Owing the filling, the retarder 4.1, 4.2 carries out its brakingfunction. The exhaust gas turbine 3 then generates a counter pressure inthe exhaust line, which counter pressure passes into the cylinder spacesand boosts the braking effect of the entire unit.

FIG. 3 shows a drive unit. It comprises an internal combustion engine 1.A main exhaust line 1.1 is connected to the internal combustion engine1. Said main exhaust line 1.1 feeds exhaust gas to an exhaust gasturbocharger 2, specifically its turbine part 2.1. The exhaust gaseswhich flow out from the turbine part 2.1 pass through a second exhaustline 1.2 to a further exhaust gas turbine 3.

A hydrodynamic unit 4 is shown. It comprises a primary wheel 4.1 and asecondary wheel 4.2. The primary wheel 4.1 has a drive connection to thefurther exhaust gas turbine 3, specifically via a first gear train 5which constitutes a step-up gear. The secondary wheel 4.2 has a driveconnection to the crankshaft 7 via a second gear train 6.

The two turbine wheels 4.1, 4.2 are rotatably mounted and thus basicallydesigned as rotors. They have the customary blades of a hydrodynamicclutch or of a hydrodynamic brake (retarder). The blades face oneanother with their free edges. The turbine wheel 4.1 acts as a primarypart and the turbine wheel 4.2 as a secondary part. The turbine wheel4.1 can be locked by means of a mechanical locking device, for exampleby means of a multi-disc clutch.

The drive unit of course comprises further components such as, forexample, a cooling device and a fan, which are, however, indicated onlyschematically here. The intake air is indicated by means of a whitearrow, while the exhaust gases are indicated by means of black arrows.

When the engine 1 runs under load in the traction mode, the exhaustgases which are fed in the main exhaust line 1.1 act on the turbine part2.1 of the exhaust gas turbocharger 2. The compressor part 2.2 of theexhaust gas turbocharger 2 compresses the sucked-in combustion air in aknown fashion.

The exhaust gases then enter the second exhaust line 1.2 and act on theturbine wheel of the further exhaust gas turbine 3. The further exhaustgas turbine 3 drives the primary wheel 4.1 of the hydrodynamic unit 4via the first gear train 5. Torque is then transmitted to the secondarywheel 4.2, specifically by means of the working fluid contained in theworking space of the hydrodynamic unit. The secondary wheel 4.2 passesthis torque on to the crankshaft 7, or to another point where it isrequired within the drive unit. The exhaust gases finally leave thedrive unit through a third exhaust line 1.3.

During the braking mode, the rotor is in an idling mode in which exhaustgases are produced only in small amounts. The further exhaust gasturbine 3 is thus acted on only to a small degree. Here, it is desirablethat it is not acted on at all, and thus also introduces no drive energyinto the drive train. For this reason it is expedient also to divert thesmall exhaust gas stream occurring during braking so that said streamcannot act on the further exhaust gas turbine 3.

However, the decisive measure is to secure the primary wheel in the waymentioned above, thus by means of some type of mechanical brake. Theprimary wheel 4.1 then acts as a stator turbine wheel. As a result, thehydrodynamic unit acts as a retarder so that no drive energy passes intothe drive train, but on the contrary energy is removed from the drivetrain so that a contribution is made to the braking work.

The turbine wheels of the hydrodynamic unit, if appropriate composed ofretarder and clutch, can be arranged inclined with respect to the axisof rotation of the hydrodynamic unit, and thus not in parallel with it.

Of course, instead of the above-mentioned gear wheels it is alsopossible to use other force-transmitting units such as chain drives.

List of reference numerals 1 Engine 1.1 Main exhaust line 1.2 Secondexhaust line 1.3 Third exhaust line 2 Exhaust gas turbocharger 2.1Turbine part of the exhaust gas turbocharger 2.2 Compressor part of theexhaust gas turbocharger 3 Exhaust gas turbine 4 First gear train 5Second gear train 7 Crankshaft 10 Parking brake

1. A method for operating a drive unit of a vehicle, the vehicleincluding an internal combustion engine having a crankshaft, an exhaustline, an exhaust gas turbine coupled to the exhaust line downstream fromthe internal combustion engine and operable to be acted upon by theexhaust line, a hydrodynamic unit coupled to the exhaust gas turbine andto the crankshaft, the hydrodynamic unit including freely rotatablerotor-turbine blade assemblies arranged within a working space, themethod comprising the steps of: in a traction mode, operating thehydrodynamic unit as a hydrodynamic clutch so that the exhaust gasturbine transmits a positive torque to the crankshaft via thehydrodynamic unit; and in a braking mode, operating the hydrodynamicunit as a retarder to retard rotation of the crankshaft by braking oneof the freely rotatable turbine blades of the hydrodynamic unit.
 2. Themethod of claim 1, wherein the braking of the freely rotatablerotor-turbine blade assemblies in the braking mode is performed using aparking brake.
 3. The method of claim 1, wherein the internal combustionengine further includes: a central processing unit, a sensor for sensingan operational state of the vehicle and for communicating a signal tothe central processing unit in accordance with the operational state ofthe vehicle; and an actuator operable to be acted upon by the centralprocessing unit to brake one of the freely rotatable rotor-turbine bladeassemblies of the hydrodynamic unit in the braking mode.
 4. The methodof claim 1, wherein the braking of one the freely rotatablerotor-turbine blade assemblies in the braking mode is performed using amulti-disc clutch.
 5. A drive unit of a vehicle, comprising: an internalcombustion engine having a crankshaft; an exhaust line; an exhaust gasturbine coupled to the exhaust line downstream in the flow of exhaustgas from the internal combustion engine; and a hydrodynamic unit coupledto the exhaust gas turbine and to the crankshaft, the hydrodynamic unitincluding: a hydrodynamic clutch having a first working space filledwith a first hydrodynamic fluid and first and second freely rotatablerotor-turbine blade assemblies arranged within the first working space;the hydrodynamic unit further including a hydrodynamic brake arrangedcoaxially with the hydrodynamic clutch, the hydrodynamic brake having asecond working space and a freely rotatable rotor and a stator arrangedwithin the second working space, the first rotatable rotor-turbine bladeassembly of the hydrodynamic clutch being fixedly coupled to the rotorof the hydrodynamic brake so that the first rotatable rotor-turbineblade assembly and the rotor are rotatable together; wherein the secondworking space is emptied of a second hydrodynamic fluid in a tractionmode so that the exhaust gas turbine transmits a positive torque to thecrankshaft via the hydrodynamic unit, and the second working space isfilled with the second hydrodynamic fluid in a braking mode to retardrotation of the crankshaft.
 6. The drive unit of claim 5, furthercomprising a bypass line connected in the exhaust line for divertingexhaust gasses in the exhaust line around the exhaust gas turbine.